How does the entities card - type: conditional work? I’ve tried multiple variations of the following…
type: entities
entities:
- type: button
...
- type: section
...
- type: conditional
conditions:
- entity: input_bool.test
state: 'on'
row:
card:
type: entities
entities:
- entitiy: ...
I’ve been searching the forum and trying different things, indentation, remove card, etc, for over 2 hrs now. 
This configuration works for me. Mind you: refresh the browser window, only after the refresh will the conditional card work properly.
In the vertical stack the top card is a custom select card (always visible), allowing to set an option (sure, no_way). Based upon the chosen option (sure) either the first conditional card (the button card) is shown that will trigger the reboot automation or (no_way) the second conditional card (the markdown card) showing the text to select the proper option above.
type: vertical-stack
cards:
- type: 'custom:select-list-card'
entity: input_select.rebootselect
icon: ''
truncate: true
show_toggle: true
scroll_to_selected: true
max_options: 5
title: Do you want to reboot?
- type: conditional
conditions:
- entity: input_select.rebootselect
state: sure
card:
type: button
tap_action:
action: toggle
entity: input_boolean.restart
- type: conditional
conditions:
- entity: input_select.rebootselect
state: no_way
card:
type: markdown
content: >-
First select the option to reboot above, then the reboot button will show
title: Select the option to reboot